diff --git a/adafruit_ina260.py b/adafruit_ina260.py
index ab38fd1..5bae822 100644
--- a/adafruit_ina260.py
+++ b/adafruit_ina260.py
@@ -186,7 +186,7 @@ def __init__(self, i2c_bus: I2C, address: int = 0x40) -> None:
 
         if self._device_id != self.INA260_ID:
             raise RuntimeError(
-                "Failed to find INA260 ID, read {self._device_id} while expected {self.INA260_ID}"
+                f"Failed to find INA260 ID, read {self._device_id} while expected {self.INA260_ID}"
                 " - check your wiring!"
             )